Muffler for an exhaust system and manufacturing method for same

ABSTRACT

A muffler for an exhaust system of an internal combustion engine, in particular in a motor vehicle, with an exhaust pipe which has an end section that is permeable for airborne sound and which is surrounded by a jacket in this end section to form a reflective chamber. To make it inexpensive to manufacture the exhaust pipe with the reflective chamber, the jacket and the end section are manufactured in one piece.

FIELD OF THE INVENTION

The present invention relates to a muffler for an exhaust system of aninternal combustion engine, especially in a motor vehicle. The inventionalso relates to a method for manufacturing a reflective chamberenclosing an end section of an exhaust pipe that is permeable forairborne sound, especially for a muffler of an exhaust system of aninternal combustion engine.

BACKGROUND OF THE INVENTION

Mufflers for exhaust systems are known in general. In certainembodiments of such mufflers, an exhaust pipe having an end section thatis permeable for airborne sound may be situated in a housing of themuffler. This end section may be sheathed by a jacket to thereby form areflective chamber. During operation of the exhaust system, exhaustgases flow through the muffler and through the exhaust pipe. Airbornesound then propagates in the exhaust gas. Airborne sound can enter thereflective chamber through the end section which is permeable forairborne sound, thereby resulting in attenuation of airborne sound in apredetermined frequency range.

For production of such reflective chambers, it is essentially possibleto push a sleeve that forms the jacket onto the outside of the endsection of the exhaust pipe and secure it on the exhaust pipe in asuitable manner.

The present invention relates to the problem of finding a method for anexhaust pipe equipped with a reflective chamber such that the method ischaracterized by inexpensive manufacturability in particular.

SUMMARY OF THE INVENTION

The invention is based on the general idea of manufacturing the jacketof the reflective chamber and the end section of the exhaust pipe in onepiece. Therefore, no separate jacket need be attached to the exhaustpipe to assemble the muffler. This integral design thus simplifiesassembly and therefore reduces the cost of manufacturing the muffler.

An embodiment in which the jacket is formed by a pipe section of theexhaust pipe that is bent or rolled back over the end section on theoutside is especially advantageous. As an alternative, it is alsopossible for the end section to be formed by a pipe section of theexhaust pipe that is bent or rolled back through the jacket on theinside. In both alternatives, both the jacket and the end section eachform an integral component of the exhaust pipe. In the starting state ofthe exhaust pipe, i.e., in the case of a starting pipe, the two pipesections which form the jacket and the end section of the finishedexhaust pipe after the sections have been bent or rolled back aresituated directly side-by-side in the longitudinal direction of thepipe. After bending or rolling back the pipe sections, the two pipesections are arranged concentrically to one another. The pipe section onthe outside then forms the jacket of the reflective chamber while thepipe section on the inside forms the end section of the exhaust pipewhich is permeable for airborne sound. The design of the reflectivechamber by bending or rolling back a pipe section of the exhaust pipecan be implemented especially inexpensively and in a manner that isreliable for the process. Furthermore, there are no tolerance problemsfor the design of the reflective chamber. Moreover, no additionaloperation is required for attaching a separate jacket to the exhaustpipe.

It is self-evident that the features mentioned above and those yet to beexplained below may be used not only in the particular combination givenbut also in other combinations or even alone without going beyond thescope of the present invention.

DETAILED DESCRIPTION OF THE FIGURES

Preferred exemplary embodiments of the present invention are depicted inthe drawings and explained in greater detail in the followingdescription, where the same reference notation refers to the same orsimilar or functionally similar components.

FIG. 1 illustrates a schematic diagram of a highly simplified basiclongitudinal section through a muffler with a reflective chamberaccording to this invention,

FIG. 2 illustrates a schematic diagram of an enlarged detail view of themuffler according to FIG. 1 in the area if the reflective chamber but ina different embodiment,

FIGS. 3 a-3 c illustrate schematic diagrams of highly simplifiedlongitudinal sections of an exhaust pipe in different manufacturingstates, and

FIGS. 4 a-4 c illustrate schematic diagrams of views like those shown inFIGS. 3 a-3 c, but in a different embodiment of the exhaust pipe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to FIG. 1, an inventive muffler 1 includes at least oneexhaust pipe 2. This exhaust pipe 2 is designed here as an outlet pipeleading out of a housing 3 of the muffler 1. The muffler 1 here alsoincludes an inlet pipe 4 and at least one connecting pipe 5. As anexample, three chambers are formed in the housing 3, namely an inletchamber 6, an outlet chamber 7 and a muffler chamber 8. The inlet pipe 4passes through the outlet chamber 7 and the muffler chamber 8 and endsin the inlet chamber 6. The at least one connecting pipe 5 passesthrough the muffler chamber 8 and connects the inlet chamber 6 to theoutlet chamber 7. The outlet pipe, i.e., the exhaust pipe 2 begins inthe outlet chamber 7 and passes through the muffler chamber 8 and theinlet chamber 6.

The inlet pipe 4 may be designed to be permeable for airborne sound inthe area of the muffler chamber 8, which may be accomplished by means ofa perforation 9, for example. This perforation 9, i.e., the permeabilityfor airborne sound, is symbolized in FIG. 1 by double arrows. Similarly,the at least one connecting pipe 5 may also be designed to be permeablefor airborne sound in the area of the muffler chamber 8. This ispreferably also accomplished with the help of a perforation 9, againsymbolized by double arrows. A suitable muffler material (not shownhere) may be arranged in the muffler chamber 8.

The exhaust pipe 2 of the inventive muffler 1 has a reflective chamber10. To this end, an end section 11 of the exhaust pipe 2 is sheathed bya jacket 12 in such a way that the reflective chamber 10 is formedradially between the end section 11 and the jacket 12. The end section11 is designed to be permeable for airborne sound, which is againsymbolized by double arrows in the figures. The permeability forairborne sound may preferably be achieved through a suitable perforation9 of the end section 11.

According to an embodiment of the invention, the jacket 12 and the endsection 11 are manufactured of one piece. This means that the jacket 12is not a separate component with regard to the end section 11 and theexhaust pipe 2 and instead the jacket 12 is an integral component of theexhaust pipe 2.

In the embodiment shown in FIG. 1, the jacket 12 is formed by a pipesection 13 of the exhaust pipe 2 which is bent back radially on theoutside over the end section 11, preferably rolled back, therebyenclosing and/or sheathing the end section 11. Furthermore, the jacket12 and/or the pipe section 13 forming the jacket 12 has a ring collector15 on its end which is remote from an opening 14 in the exhaust pipe 2,said ring collar protruding inward radially and being in contact withthe exhaust pipe 2. In this way, the reflective chamber 10 is closed onthe end remote from the opening 14. On the end facing the opening 14,the reflective chamber 10 is necessarily sealed by the seamlesstransition between the interior end section 11 and the exterior jacket12.

The ring collar 15 may essentially be in loose contact with the exhaustpipe 2. Leakage is not critical here. Essentially however it is possiblethrough suitable measures to mount the ring collar 15 in an airtightmount on the exhaust pipe 2 and/or to attach it to the exhaust pipe 2.For example, this may be accomplished through an appropriate flangingand/or by soldering and/or welding.

In the alternative embodiment illustrated in FIG. 2, the end section 11which is perforated or permeable for airborne sound is formed by thepipe section 13 which in this case is bent back radially on the insidethrough the jacket 12, especially being rolled back to thereby form thereflective chamber 10. In this variant the ring collar 15 protrudesradially outward away from the end section 11 and is in contact with theexhaust pipe 2 on the inside. Here again essentially a loose or airtightand/or tight contact between the ring collar 15 and the exhaust pipe 2is/are possible.

Preferred embodiments of a method for producing the reflective chamber10 on the exhaust pipe 2 are explained in greater detail below.

FIG. 3 a illustrates a starting state with a starting pipe 2′ having apipe opening 16. A first pipe section 13 begins at this pipe opening 16,with a second pipe section 17 being connected thereto.

According to FIG. 3 b, in a first process step, the second pipe section17 is made permeable for airborne sound, symbolized here again by thedouble arrows. The second pipe section 17, for example, is provided witha perforation 9.

Then the first pipe section 13 is bent back on the outside over thesecond pipe section 17, preferably by rolling it back, thereby achievingthe state illustrated in FIG. 3 c. The ring collar 15 may be formed bybending back the first pipe section 13 or subsequent thereto and broughtinto contact with the exhaust pipe 2. Then the finished exhaust pipe 2is obtained, with the two pipe sections 13, 17 starting at the opening14 of the exhaust pipe 2. The second pipe section 17 on the inside thenforms the end section 11 while the first pipe section on the outsideforms the jacket 12. Then the reflective chamber 10 is formed betweenthe end section 11 and the jacket 12.

According to FIGS. 4 a through 4 c, the exhaust pipe 2 equipped with thereflective chamber 10 may also be produced as described below.

In the starting state according to FIG. 4 a, the starting pipe 2′ againhas the pipe opening 16, the first pipe section 13 and the second pipesection 17.

In a first processing step according to FIG. 4 b, the first pipe section13 is then designed to be permeable for airborne sound and to this endis equipped in particular with a perforation 9.

Following that, according to FIG. 4 c, the first pipe section 13 is bentback on the inside through the second pipe section 17, preferably byrolling it back. At the same time or subsequently, the ring collar 15 isformed and brought into contact with the exhaust pipe 2. In the finishedstate of the exhaust pipe 2, the two pipe sections 13, 17 here againbegin at the opening 14. The first pipe section 13 is situated on theinside, forming the end section 11 of the exhaust pipe 2, while in thisvariant the second pipe section 17 is situated on the outside andsubsequently forms the jacket 12. The reflective chamber 10 is againformed between the jacket 12 and the end section 11.

Suitable tools or machines are known for bending or rolling back a pipesection. This bending or rolling process can be designed to beadequately reliable, in which case comparatively narrow shape tolerancescan be maintained in particular. The integral design of the reflectivechamber 10 on the exhaust pipe 2 makes implementation of such areflective chamber 10 comparatively inexpensive. In particular, thiseliminates the need for any additional processing steps for attaching ajacket designed as a separate component to the exhaust pipe 2.

1. A muffler for an exhaust system of an internal combustion engine of amotor vehicle, comprising: an exhaust pipe having an end section that ispermeable for airborne sound and is sheathed by a jacket in this endsection to form a reflective chamber, wherein, the jacket and the endsection are made of one piece.
 2. The muffler according to claim 1,wherein the jacket is formed by a pipe section that is bent or rolledback over the end section on the outside.
 3. The muffler according toclaim 1, wherein the end section is formed by a pipe section that isbent or rolled back through the jacket on the inside.
 4. The muffleraccording to claim 1, wherein the jacket or the end section has a ringcollar which is in contact with the exhaust pipe and protrudes radiallyon its end remote from an opening in the exhaust pipe.
 5. The muffleraccording to claim 1, wherein the end section perforated.
 6. The muffleraccording to claim 1, wherein the exhaust pipe is an outlet pipe leadingout of a housing of the muffler.
 7. A method for manufacturing anexhaust pipe for a muffler for an exhaust for an internal combustionengine, the muffler having a reflective chamber surrounding an endsection of an exhaust pipe, said end section being permeable forairborne sound, the method comprising: making an outlet pipe, which hasa first pipe section beginning at a pipe opening and a second pipesection connected to the first pipe section, permeable for airbornesound in the second pipe section, and bending the first pipe sectionback over the second pipe section on the outside, wherein, the two pipesections begin at an opening in the exhaust pipe with the second pipe onthe inside forming the end section and the first pipe section on theoutside forming a jacket enclosing the reflective chamber.
 8. The methodaccording to claim 7, wherein the bending back operation comprises arolling process.
 9. The method according to claim 7, wherein therespective pipe section is perforated to make it permeable for airbornesound.
 10. A method for manufacturing an exhaust pipe for a muffler foran exhaust for an internal combustion engine, the muffler having areflective chamber surrounding an end section of an exhaust pipe, saidend section being permeable for airborne sound, the method comprising:making an outlet pipe, which has a first pipe section beginning at apipe opening and a second pipe section beginning at the first pipesection, permeable for airborne sound in the first pipe section, and,bending the first pipe section back through the second pipe section onthe inside, so that the two pipe sections begin at an opening in theexhaust pipe, wherein, the first pipe section on the inside forms theend section, while the second pipe section on the outside forms a jacketsurrounding the reflective chamber.
 11. The method according to claim10, wherein the bending back operation is embodied as a rolling process.12. The method according to claim 10, wherein the respective pipesection is perforated to make it permeable for airborne sound.